Vehicle Refrigeration Compressor Control Without a Suction Pressure Sensor
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Solution Overview
Problem
Existing refrigeration cycle devices for vehicles with capacity-variable compressors face challenges in accurately estimating suction pressure without increasing the number of parts, leading to deviations in estimated suction pressure from actual values, especially during transient states and high engine loads.
Innovation Solution
A refrigeration cycle device that includes a capacity-variable compressor, an evaporator, thermal load detection, refrigerant flow amount detection, and pressure estimation means to calculate and control the preset suction pressure based on thermal load and refrigerant flow, eliminating the need for a suction pressure sensor and simplifying the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a suction pressure sensor is installed to correctly detect the suction pressure of the compressor, then the measurement precision of suction pressure is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent uses the evaporator temperature sensor as an intermediary to indirectly measure the suction pressure. Instead of directly measuring suction pressure with a pressure sensor, the system measures evaporator temperature and uses it to estimate suction pressure through the relationship between temperature and pressure in the refrigeration cycle. This intermediary approach avoids adding complex pressure sensing components while maintaining measurement capability.
Solution Approach 2:
The patent replaces the mechanical pressure sensor system with a thermal measurement system. By substituting the direct mechanical pressure detection mechanism with a temperature-based estimation approach, the system eliminates the need for additional pressure sensing hardware, thereby reducing device complexity while achieving the measurement objective.
2Device complexity
If the suction pressure is estimated from evaporator pressure, then the device complexity is reduced, but the measurement precision of suction pressure deteriorates
Solution Approach 1:
The patent changes the measurement parameter from direct pressure measurement to temperature measurement. By measuring evaporator temperature and using it to infer suction pressure characteristics, the system achieves a balance between simplicity and accuracy. The temperature parameter serves as a reliable proxy that reflects suction pressure conditions without requiring complex pressure sensing arrangements.
3Reliability
If the refrigerant discharge capacity is controlled during transient states, then the reliability of engine operation is improved, but the loss of time in control response increases
Solution Approach 1:
The patent implements preliminary action by detecting transient states in advance and preemptively adjusting the refrigerant discharge capacity before the transient condition fully develops. The control system monitors parameters such as vehicle speed changes and compressor rotational speed variations, and when a transient state is detected, it immediately adjusts the capacity-varying unit to prevent excessive load fluctuations, thereby maintaining engine reliability while minimizing response time delay.
Data Source
AI summary
In a refrigeration cycle device with a capacity-variable compressor, a preset suction pressure that serves as a target value of a refrigerant suction pressure of the compressor is calculated and a refrigerant discharge capacity of the compressor is controlled by operating a capacity varying portion such that the suction pressure of the compressor is appreciated to the preset suction pressure. A thermal load detection portion is configured to detect a thermal load of a refrigeration cycle, and a refrigerant flow amount detection portion is configured to detect a flow amount of refrigerant circulating through the refrigeration cycle. In the refrigeration cycle device, a pressure at a predetermined part of the compressor is estimated based on the thermal load detected by the thermal load detection portion and on the flow amount detected by the refrigerant flow amount detection portion.